This Phase I trial will assess the effects of expressing recombinant IDS in 2 adults with the "mild" form of Hunter syndrome. Peripheral blood lymphocytes (PBL) will be harvested by aspheresis and then transduced ex vivo with retrovirus vector L2SN (FDA BB-IND #5370). Transduced PBL will be then infused on a monthly basis. Evaluation of patients will include serial measurement of IDS enzyme, assessment of urine glycosaminoglycans, measurement of liver and spleen volumes by CT scan, pulmonary function tests, echocardiography and EKG.